Adding an additive to a polymer used as a raw material in an extrusion molding, blow molding, rotational molding, or injection molding process to give various functions to molded products has been conventionally considered.
Patent Document 1 proposes a composition which constitutes a liquid-in-solid polymer emulsion at room temperature, the composition including: a thermoplastic polymer (A); 0.1 to 50 parts by weight of a block copolymer (B) mixed with 100 parts by weight of the theinioplastic polymer (A), the block copolymer (B) being phase-separated from the thermoplastic polymer (A); and 0.1 to 20 parts by weight of a liquid compound (C) dispersed in 100 parts by weight of the mixture of the thermoplastic polymer (A) and the block copolymer (B), wherein the block copolymer (B) contains a block (b1) having high compatibility with the thermoplastic polymer (A) but low compatibility with the liquid compound (C) and a block (b2) having high compatibility with the liquid compound (C) but low compatibility with the thermoplastic polymer (A), the liquid compound (C) has low compatibility with the block (b1) and the thermoplastic polymer (A) but high compatibility with the block (b2), the liquid compound (C) being phase-separated from the thermoplastic polymer (A) and being liquid at 100° C. or lower, the liquid compound (C) is enclosed by the block copolymer (B) by a surfactant-like function of the block copolymer (B), the thermoplastic polymer (A) is a polyolefin polymer, the block (b1) is a polyolefin block and the block (b2) is a polystyrene block, and the block copolymer (B) is at least one selected from the group consisting of a polystyrene-polyethylene/propylene) block copolymer, a polystyrene-poly(ethylene/butylene) block copolymer, a polystyrene-poly(ethylene/propylene)-polystyrene block copolymer, a polystyrene-poly(ethylene/butylene)-polystyrene block copolymer, and a polystyrene-poly(ethylene-ethylene/propylene)-polystyrene block copolymer. However, Patent Document 1 fails to describe a liquid compound (C) which has low compatibility with the block (B2).
Adding a halogen compound or phosphor compound is known as a method for giving flame retardancy to polyolefin. Patent Document 2 discloses the following examples of the halogen compound: polybrominated diphenyl oxide (DE60F), decabromodiphenyl oxide (DBDOP), bis(2,3-dibromopropyl ether) of bisphenol A (PE68), brominated epoxy resin, ethylene-bis(tetrabromophthalimide) (BT93), 1,2-bis(tribromophenoxy)ethane (FF680), and tetrabromo-bisphenol A (SAYTEX® RB100). Among the polybrominated diphenyl oxides, compounds having 5 and 8 bromine atoms are accumulative and therefore do not comply with the RoHS Directive. Decabromodiphenyl oxide (DBDOP) was withdrawn from the RoHS Directive materials but has a melting point of 300° C. or higher and a large grain size of 4 μm and is therefore not suitable for uses as thin films or fine fibers.
Patent Document 2 discloses the following examples of the phosphor compound: tris(2,4-di-tert-butylphenyl)phosphite, bis(2,4di-tert-butyl-6-methylphenyl)ethyl phosphite, 2,2′,2″-nitrilo [triethyl-tris-(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite], tetrakis(2,4di-butylphenyl) 4,4′-biphenylene-diphosphonite, tris(nonylphenyl)phosphite, bis(2,4di-tert-butylphenyl)pentaerythrityl diphosphite, 2,2′-ethylidenebis(2,4di-tert-butylphenyl)fluorophosphite, 2-butyl-2-ethyl-propan-1,3-diyl 2,4,6-tri-tert-butylphenyl phosphite, ammonium polyphosphate (APP) or (HOSTAFLAM® AP750), resorcinol diphosphate oligomer (RDP).
Patent Documents 3 and 4 disclose polypropylene fibers containing 0.5 w % or more of a phosphoric ester flame retardant and 0.5 w % or more of a NOR-type HALS. These patent documents were filed after the disclosure of Patent Document 2. Also, the disclosures of Patent Documents 3 and 4 are cumulative to the disclosures of Patent Document 2. Patent Document 2 also fails to define the content of phosphor which is an effective constituent for flame retardancy but only defines the content of phosphoric ester as being 0.5 w %, which is a 1/10 of a common value in the art, without evidence, thus lacking authenticity.
Trimethyl phosphate and triethyl phosphate of high phosphor content, 17 w % or higher, are most preferable as a flame retardant because of their low molecular weights. However, they are liquid at room temperatures and have poor compatibility with polyolefin when they are liquid and are therefore separated from polyolefin. Thus, in general, none of trimethyl phosphate and triethyl phosphate can be used as a flame retardant for polyolefin. Tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, cresyl dixylenyl phosphate, which are flame retardants having slightly greater molecular weights and low phosphor contents, about 8 w %, are also liquid at room temperatures and therefore generally cannot be used as a flame retardant for polyolefin. Meanwhile, triphenyl phosphate is solid at room temperatures but has a melting point of 49° C. and therefore melts when mixed with polyolefin. Thus, triphenyl phosphate cannot be used as a flame retardant for polyolefin. Tris(chloropropyl)phosphate and tris(dichloropropyl)phosphate are liquid at room temperatures, and tris(tribromoneopentyl)phosphate is also liquid at polyolefin process temperatures. They cannot be used as a flame retardant for polyolefin in general.
Patent Document 1: Gazette of PCT/JP2006/313824
Patent Document 2: Gazette of U.S. Pat. No. 6,472,456
Patent Document 3: Gazette of Japanese Patent No. 3540759
Patent Document 4: Gazette of Japanese Patent No. 3679738